Removal of wax from hydrocarbon oil



June 23,1936 R. MANLEY ET Al. 2,045,305 vREMOVALv @F. WAX FROM HYDROCARBON OIL Filed Allg. 22, 1933 BY www /w ATTORNEY Patented June 23, 1936 REMOVAL F WAX (lJOM HYDROCARBON -Robert E. Manley, Bernard Y. McCarty, and Howard H. Gross, Beacon, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of vDelaware Application August 22, 1933, Serial No. 686,244

g `13 Claims.l (01.196-19) This invention relates to theremoval Vof wax from hydrocarbon oil, and more particularly'to dewaxing mineral lubricating oil.l

The invention broadly contemplates a process for removing wax from wax-bearing hydrocarbon oil wherein the wax-bearing oil is treated with al relatively small amount of a'carbonaceous material derived from cracked petroleum tar, and which is adapted to modify Wax crystal uformation and thereby facilitate separation of the wax from the oil. The wax-bearing mixture is then diluted with a suitable solvent, such as petroleum naphtha, and chilled to precipitate the wax. 'Ihe wax thus precipitated is removed by mechanical means, or by cold settling, following which the diluent is removed from the resulting dewaxed oil.

In the drawing, the single figure is a ow sheet of the process of the present invention. .Y y

We have discovered that cracking still residue or the tar resulting from the cracking of petroleum oil for the production of motor fuel, when l subjected to further decomposition or recracking,

contains certain constituents which are adapted to facilitate the removal of wax constituents from mineral lubricating oil, when radded thereto in relatively small proportions. Cracked pressure tar herein described is that produced according to the method disclosed and claimed in the copending application of R. E. Manley and H. H. Gross, Serial No. 658,668, filed February 25, 1933, and wherein the addition of this material as a concentrated pour point depressant to a lubricating oil is described and claimed.

The addition of this material to a wax-bearing solution modifies the growth of the wax crystals precipitated from the solution upon chilling. It appears to inhibit the precipitation of wax in the form of a network of interlocking needle crystals as is the normal tendency upon precipitation from cold solution. Instead the wax tends to be precipitated in discrete particle form. The presence of this modifying material thus results in the formation of a crystal mass of wax which is more readily removed from the oil by cold settling.

We have found that cracked petroleum tar may be converted to a pitch, representing about 50% or 60% of the original tar, which will contain substantial amounts of the desired constituents. The method of conversion comprises subjecting the tar resulting from the ordinarycracking' operation to further cracking at temperatures of about 800 to around l000 F., and under pressures which may range from substantially above atmospheric to around 400 pounds or higher.

The particular conditions of temperature and pressure, however, may be varied, depending upon the nature of the tar and, to some extent, upon the yield and nature of the products desired. Thus,it has' been found that the cracked tars resulting from the cracking of mineral oil derived from different crude petroleum sources require somewhat different treatingconditions to convert them into a pitch'` containing the desired constituents. Y

Referring to the drawing, the pitch 'I0 vthus produced by the conversion of cracked' petroleumV tars is then advantageously mixed in extractor and agitator I I with a suitable Aquantity of a rela-v tively viscous mineral oil I2 such` as a lubricating fraction,` for example, in the proportions of about one part of pitch to one part of oil. This mixture is then subjected to heating for about thirty'minutes at a temperature of around 320 F. in the presence of a comminuted solidcatalytic material I3, such as a diatomaceous earth, fullers earth, or acid-treated clay, for example. TheV temperature of this treatment may vary from around 300 to 400 F. and the treatment may,` if' desired, be carried out in the presence of steam.

The resulting mixture of liquid and solid'catalytic material, while hot, is subjected to filtration in filter I4 to remove the solid matter vand produce a filtrate I5 of oil and dissolved constituents which have been extracted from the pitch, and thusseparated from the undissolved solids I 6. This filtrate solution comprises the wax crystal modifying material in solution and adapted rto be added to wax-bearing oil to facilitate the removal of wax therefrom.

This modifying material recovered from the converted cracked tar, dissolved in the solvent oil, may bel added to wax-bearing oil I1 which is to be dewaxed by filtration, centrifuging, cold settling, or by other methods. The presence of this material in the wax-bearing mixture results in very greatly increasing filtering rates, or in materially improving the degree of wax separation by cold settling. It materially reduces the dewaxing losses by improving the degree of separation realized between the oil constituents and the wax constituents of the wax-bearing mixture. This is further illustrated by referenceto the following examples: Y

' A quantity of the foregoing solution of modifying material in mineral oil was added to a cylinder stock distillate havinga viscosity of about 73".Saybolt Universal seconds at 210 F., the pro-4 portion of modifying solution comprising about 6% by volume of the wax-bearing distillate. This mixture was then diluted with a light petroleum naphtha from dewaxing solvent tank IB in the proportion of about four parts of naphtha to one part of wax-bearing mixture.

The resulting solution was then cooled in chiller I9 to a temperature of around 20 to 25 F. and subjected to settling at these temperatures. Settling of the wax constituents from the mixture rapidly occurred. The supernatant liquid layer of oil and solvent was drawn off, and the solvent removed therefrom by distillation. The

resulting oil had a pour test of 0 F. The dewaxing loss, as represented by the lower layer composed of waxy constituents settled out of the oil, constituted about 41% of the original wax-bearing oil.

When subjecting a mixture of the same waxbearing oil with the same proportion of light petroleum naphtha to settling but without the addition of the modifying material from the cracked petroleum tar, a substantially smaller yield of oil having the same pour test was produced; that is to say, the dewaxing loss in this instance constituted about 53% of the original wax-bearing oil.

This same wax-bearing stock, when mixed with substantially the same proportion of the constituents recovered from the tar, and when diluted in substantially the same proportion of light petroleum naphtha, was subjected to dewaxing by pressure filtration in lter 20 in the presence of a filter-aid material. It was found that the filtering rates of this mixture were increased several times over that obtaining when filtering a similar wax-bearing mixture but which did not contain the modifying material. The filtrate separated from the solids including wax 2l is passed to distillation equipment 22, where retained solvent 23 is removed from the dewaxed oil 24.

While certain temperature and pressure conditions, as well as liquid proportions, have been set forth in the foregoing examples, the invention is not restricted to these particular conditions since they may be varied as desired, depending upon the nature of the wax-bearing oil undergoing treatment and upon the extent of the' dewaxing required.

While we have described extracting a modifying material of desired characteristics from converted cracked petroleum tar by treatment with a lubricating oil fraction of mineral oil, it is contemplated that, in many instances, other fractions of mineral oil or solvents, capable of extracting these constituents from the pitch may be used. It is contemplated also that the converted tar or pitch may be added directly to the wax-bearing oil, or a portion thereof, and the resulting mixture subjected to digestion for a short interval of time at temperatures of around 320 or 350 F., either with or without the presence of clay, in order to extract the desired constituents, and thus avoid the use of an intermediate extracting solvent. Where a portion only is treated, it may then be added to the main body of Wax-bearing oil and thoroughly mixed therewith. The resulting mixture, after dilution with naphtha or other diluent or solvent, may be cooled and chilled to the desired dewaxing temperature in order to precipitate the wax. The wax constituents will be precipitated and separated from the oil along with the insoluble portions of the extracted modifying material. In this way, the combined procedure of recovering the desired modifying material from the converted tar, its addition to the wax-bearing oil, and the subsequent removal of the wax, is simplied.

It is also contemplated that other diluents besides naphtha may be employed in the dewaxing step, such as mixtures of acetone and benzol, or mixtures of other selective and non-selective solvent liquids which are capable of serving as satisfactory dewaxing solvent.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim- 1. The method of separating wax from waxbearing oil comprising mixing with the oil a hydrocarbon material of limited solubility in the oil derived from recracked cracked petroleum tar and containing oil soluble constituents adapted to modify wax crystal formation to thereby facilitate removal of the wax from the oil, adding a diluent to the oil in sufficient proportions to produce a relatively non-viscous mixture at low temperatures, chilling the resulting mixture to precipitate the wax, removing the wax thus precipitated, and recovering the diluent from the dewaxed oil.

2. The method of separating wax from waxbearing oil comprising mixing with the oil a hydrocarbon material derived from recracked cracked petroleum tar and containing oil soluble constituents adapted to modify wax crystal formation to thereby facilitate removal of the wax from the oil, other constituents of the material being substantially insoluble in the oil, diluting the oil by the addition thereto of a substantial proportion of light petroleum naphtha, chilling the resulting mixture to precipitate the wax, removing the wax thus precipitated, and recovering the diluent from the dewaxed oil.

3. The method of separating wax from waxbearing oil comprising mixing said filtrate liquid with the Wax-bearing oil, a filtrate obtained from contact filtration at elevated temperature in the presence of a comminuted adsorbent material of a mineral lubricating oil mixture with a pitch derived from recracked cracked petroleum tar and of limited solubility in the oil, the filtrate being mixed in the proportion of about 5% to 10% of filtrate by volume of the wax-bearing oil, diluting said mixture to facilitate subsequent removal of the wax, chilling the resulting mixture to precipitate the wax, removing the wax thus precipitated, and recovering the diluent from the dewaxed oil.

4. The method of separating wax from waxbearing oil comprising mixing the wax-bearing oil with a suitable proportion of pitch of limited solubility in the oil produced by subjecting cracked petroleum tar to additional cracking, subjecting said mixture to digestion at elevated temperature to extract from the pitch constituents adapted to precipitate wax from cold solution in a readily separable form, diluting the digested mixture to facilitate subsequent removal of the wax, chilling the resulting mixture to precipitate the wax, removing the wax thus precipitated, and recovering the diluent from the dewaxed oil.

5. The method of separating wax from waxbearing oil comprising mixing a portion of the wax-bearing oil with about an equal volume of pitch produced by subjecting cracked petroleum tar to additional cracking such as to concentrate oil soluble constituents adapted to modify Wax crystal formation and render other constituents substantially oil insoluble, subjecting said rriixture to digestion at elevated temperature to extract from the pitch constituents adapted to precipitate Wax from cold solution in a readily separable form, mixing the digested oil with the main body of Wax-bearing oil, diluting the digested mixture to facilitate subsequent removal of the Wax, chilling the resulting mixture to precipitate the Wax, removing the Wax thus precipitated, and recovering the diluent from the dewaxed oil.

6. The method of dewaxing a Wax bearing oil, comprising mixing with the oil a small proportion of a concentrated pour point depressant material derived from a recracked pressure tar which is primarily insoluble in the oil but which contains oil soluble pour depressant material which has the property of materially increasing the rate of filtration of an oil containing Wax precipitated in the presence of the pour point depressant material, chilling the mixture to precipitate the wax, and then filtering to remove the precipitated Wax from the oil.

7. The method of dewaxing a Wax bearing oil, comprising mixing with the oil a concentrated pour point depressant material derived from a recracked pressure tar Which is primarily insoluble in the oil but Which contains oil soluble pour depressant material, the latter having the property of increasing the rate of filtration of an oil containing Wax precipitated in the presence of the pour point depressant material, chilling the mixture to precipitate the Wax, and then filtering in the presence of a filter-aid material to remove the precipitated Wax and filter-aid material from the oil.

8. The method of dewaxing a wax bearing oil, comprising mixing with the oil a solvent highly selective between the normally liquid and normally solid constituents of the oil and in which the normally liquid constituents are soluble at lowered temperatures While the normally solid constituents are substantially completely insoluble, together with a pour point depressant material derived from a recracked pressure tar which is primarily insoluble in the oil but which contains oil soluble pour depressant material which has the property of increasing the rate of filtration of an oil containing Wax precipitated in the presence of such a selective solvent and the pour point depressant material, chilling the mixture to precipitate the Wax, filtering to remove the precipitated Wax, and recovering the solvent from the ltrate.

9. The method of dewaxing a Wax bearing oil, comprising mixing with the oil a solvent mixture highly selective between normally liquid and normally solid constituents of the oil and having substantially the highly selective solventi action of a mixture of acetone and benzol, to-v gether with a pour point depressant material derived from a recracked pressure tar which is primarily insoluble in the oil but which contains oil soluble pour depressant material which has the property of increasing the rate of filtration of an oil containing Wax precipitated in the presence of such a selective solvent mixture and the pour point depressant material, chilling the mixture to precipitate the Wax, filtering to removek the precipitated wax, and recovering the solvent from the filtrate.

10. The method of dewaxing a Wax bearing oil, comprising mixing with the oil a solvent mixture comprising acetone and benzol, together kwith a Wax crystal modifying material derived from a recracked pressure tar which is primarily insoluble in the oil but which contains oil soluble pour depressant material and which has the property of increasing the rate of filtration of an oil containing Wax precipitated in the presence of such solvent mixture and the modifying material, chilling the mixture to precipitate the Wax, filtering to remove the precipitated wax from the oil-solvent liquid, and recovering the acetone and benzol from the filtrate.

11. The method of dewaxing a Wax bearing oil, comprising mixing with the oil a mineral lubricating oil extract which is concentrated in pour point depressant material derived from a recracked pressure tar which is primarily insoluble in the oil but which contains oil soluble pour depressant material having the property of increasing the rate of filtration of an oil containing wax precipitated in the presence of the pour point depressant material, chilling the mixture to precipitate the Wax, and filtering to remove the precipitated Wax from the oil.

12. 'Ihe method of dewaxing a Wax bearing oil, comprising mixing With the oil a solvent kextract of recracked cracking still residue of limited solubility in the oil, the extract being concentrated in oil soluble Wax crystal modifying material having the property of increasing the rate of filtration of an oil containing Wax precipitated in the presence of such material, chilling the mixture to precipitate the Wax, and filtering to remove the precipitated wax from the oil.

13. The method of dewaxing a Wax bearing oil, comprising mixing With the oil a mineral lubricating oil extract of a pitch derived from recracking pressure tar of limited solubility in the oil, the extract containing a high concentration of oil soluble wax crystal modifying material having the property of increasing the rate of filtration of an oil containing wax precipitated in the presence of such material, chilling the mixture to precipitate the Wax, and filtering to remove the precipitated wax from the oil.

ROBERT E. MANLEY. BERNARD Y. MCCARTY. HOWARD I-I. GROSS. 

